In one type of conventional office chair, such chairs are provided with molded seat and back panels which are supported together by a chair frame. Typically, the seat and back panels have a unitary molded construction. Some of such chairs have been provided with tilt control mechanisms so that the back panel articulates relative to the seat panel.
In other conventional office chairs, such chairs eliminate back panels or molded panels since these have a greater rigidity, instead, the seat and back assemblies incorporate flexible or cushioned materials to support the chair occupant in an effort to improve the comfort for the user. Many different features have been implemented in these office chairs including padded seats, mesh suspension fabrics and lumbar support pad assemblies to provide additional support to the lumbar of the chair occupant.
It is an object of the invention to provide an improved construction for chairs having molded seat and/or back panels.
The invention relates to an improved chair back which is formed of a molded construction that substantially differs from known chair backs using a single molded material that provides a uniform, relatively rigid back construction which unitary back construction can be undesirable. However, the chair back of the invention uses multiple mold shots of mold materials to develop different performance characteristics in different areas of the chair back.
In particular, the chair back has a generally rectangular shape and integrally includes two, downwardly projecting uprights which are configured to pivotally connect to a chair base. The uprights rigidly support the chair back along the opposite left and right side edges thereof. The chair back further comprises a sheet-like support panel extending between the uprights at the side edges, which is vertically enlarged and configured to support the chair back of the occupant. To define different performance characteristics in the chair back, the chair back has the appearance of a unitary molded panel, but is formed from multiple mold shots which preferably are performed at multiple stations on a mold tool.
In this regard, a first mold shot is performed to construct right and left structural components, preferably formed as generally L-shaped uprights that are sufficiently rigid so as to pivotally connect to the chair base. These left and right uprights provide significant structural rigidity to the left and right sides of the chair back.
In the second mold shot, the left and right uprights are overmolded with a second material to further build up another layer on the left and right sides of a back frame to form vertical or upright frame sections as well as form upper and lower cross members. This second mold shot generally forms an annular frame for the chair back that is defined by the overmolded uprights and the integrated cross members which surround an open interior of the chair back so as to define the visual appearance of an annular or peripheral back frame.
Preferably, the second mold shot also includes the formation of an intermediate web extending crosswise between the upright frame members to form a lumbar support structure or support pad which is located in the open interior and is spaced vertically from the upper and lower cross members or frame sections. The upright frame sections and horizontal cross members have a greater thickness and are less flexible so as to support loads on the chair back generated by the chair occupant.
After the second shot is completed, third and fourth mold shots are performed, preferably at the same time, although the shots are considered to be separate since they form different structures of the chair back. As such, the third and fourth mold shots also may be performed sequentially.
More particularly, the material for shot three is the same as the mold material for shot number two to ensure chemical bonding with the material of the second mold shot. The third shot forms an encapsulating wall around the vertical and horizontal frame sections to define the final, finished surfaces for these structures. The inner boundary of the third shot does not extend inwardly beyond the peripheral back frame into the interior region of the back which interior region would remain open and only the intermediate web structure. However, the fourth shot encloses this interior region as discussed below.
In particular, the fourth shot forms a thin sheet in the interior region extending from the inner boundary of the third shot encapsulating the vertical and horizontal frame structures. The fourth shot essentially defines a relatively thin, sheet-like suspension structure or interior panel that encloses the open interior, encapsulates the intermediate web and provides a support region which has greater flexibility in comparison to the frame structure.
By providing multiple mold shots to form different areas of the chair back, different performance characteristics are generated including the provision of a peripheral frame providing structural rigidity to the chair back, a lumbar support panel which uses the intermediate web to provide localized support to the lumbar region of the chair occupant, and a thin sheet-like panel extending between the frame and enclosing the interior region defined between the peripheral frame to provide a more flexible and pliant surface in contact with the occupant's back.
The invention relates to the chair structure itself as well as the method for constructing same.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.